Veterinarians commonly prescribe ivermectin for dogs to prevent heartworm infections and to treat a variety of highly contagious mites. When used correctly, it is an extremely safe and effective drug.
If used incorrectly, however, ivermectin has the potential to cause serious side effects. To make sure you are using this drug safely, you should educate yourself about it and administer it only under the direction of a trusted veterinarian.
What Is Ivermectin?
Ivermectin is a common anti-parasitic drug available in oral, topical and injectable formulations. It works by targeting the nervous systems of a variety of parasites.
At safe doses, it has the ability to kill immature heartworms, most intestinal worms, most mites and some species of lice. It does not kill tapeworms, flukes, fleas or ticks.
It also does not kill adult heartworms, but it does shorten their lives and prevent them from reproducing.
What Are the Potential Side Effects of Ivermectin in Dogs?
Ivermectin does not typically produce side effects at the low doses veterinarians use for heartworm prevention. While still rare, side effects are more likely with the higher doses used for treating mites and other parasites.
These side effects are most common in dogs that possess a mutation in the multidrug resistance gene, which is often referred to as the MDR1 gene.
Potential ivermectin side effects include the following:
- Decreased appetite.
- Dilated pupils.
- Change in behavior.
If you suspect your dog is experiencing a reaction to ivermectin, contact your veterinarian or the local veterinary emergency center immediately.
What Is the Usual Ivermectin Dosage for Dogs?
The recommended dose of ivermectin varies depending on the condition being treated. For the prevention of heartworm infection, a typical dose is 6 micrograms per kilogram, or 2.73 micrograms per pound, by mouth once a month in dogs and puppies greater than six weeks of age.
Higher doses of ivermectin than those used for heartworm prevention are required to treat mites including mange mites and ear mites.
When using ivermectin as a demodectic mange treatment for generalized disease, the Merck Veterinary Manual recommends using a dose of 300 to 600 micrograms per kilogram daily until the dog has tested negative twice via consecutive skin scrapings taken at monthly intervals.
For scabies, ear mites and other skin mites, the recommended dose is 300 micrograms per kilogram every one to two weeks as needed. Because some dogs cannot tolerate high doses of ivermectin, veterinarians often start with a test dose of 100 micrograms per kilogram and gradually increase the amount given until the dog is receiving the recommended dose.
Is IT Safe for All Dogs?
At the very low doses used for heartworm prevention, ivermectin is a safe drug for dogs. The doses used to treat skin mites are also well within the safe range for most dogs, but these doses can cause problems in certain individuals including those that possess the MDR1 mutation that causes ivermectin sensitivity.
While this mutation can occur in any dog, it is most common in members of the following breeds according to the Washington State University College of Veterinary Medicine:
- Australian Shepherd.
- Long-haired whippet.
- Silken windhound.
Increased sensitivity to ivermectin can also occur in animals without this genetic mutation. Young puppies are more likely than adult dogs to be sensitive to ivermectin because their blood-brain barriers are not yet fully developed.
Additionally, adult dogs with health conditions that disrupt the integrity of the blood-brain barrier may be more sensitive than healthy dogs to ivermectin.
Is There a Way to Prevent Ivermectin Toxicosis?
The best way to prevent accidental overdose is to keep all products containing ivermectin away from your dog and to use these products only as directed.
Additionally, you should prevent your dog from eating the feces of horses, cows and other farm animals treated with ivermectin. The feces of these animals can contain enough of the drug to sicken or kill a dog.
To prevent toxicosis when using relatively high doses of ivermectin to treat skin mites, many veterinarians recommend using low test doses of the drug before beginning a treatment course. This is especially important in dogs with risk factors for ivermectin sensitivity.
In addition, owners of dogs from vulnerable breeds may elect to have their pets tested for the MDR1 mutation that causes ivermectin sensitivity. This test is available from the Washington State University College of Veterinary Medicine.
Is It Safe to Give a Dog Ivermectin Labeled for Livestock?
Ivermectin products labeled for livestock are much more concentrated than those intended for small animals, so it is much easier to give a dangerous overdose of these products. To keep your pet safe, you should only use products labeled for dogs unless advised to do otherwise by a veterinarian.